The present invention relates to a method of setting up a connection between a first terminal and a second terminal over an Integrated Services Digital Network (ISDN) link providing one or more bearer channels that allow a user-selected protocol, the terminals supporting a plurality of possible software protocols for use on said bearer channels. The invention also relates to an application resource system for setting up a connection between a first terminal and a second terminal over an ISDN line.
When a connection is to be set up between two terminals, over an Integrated Services Digital Network (ISDN) link providing one or more bearer channels that allow a user-selected protocol, a Call Setup message is being sent from a first Application Resource System to a second Application Resource System. It is a problem that different types of ISDN protocols can be used in different parts of the system. There is a general protocol according to CCITT q931, which is the base for the ISDN protocol family. Other ISDN protocols that can be used such as DSS1, ISDN S2 and ATandT 5ESS, are modifications of the general ISDN protocol q931.
Making adoption to a new type of ISDN protocol on an existing system is a costly procedure which takes a lot of man-hours to achieve. The software units involved are normally very complex and tricky to work with.
What is needed is therefore a software system structure that supports fast and easy implementation of different ISDN protocols to achieve low development cost.
This object is solved by the method in accordance with the invention, wherein the protocol software is separated into a generic module containing generic ISDN encoding/decoding protocols and into protocol specific modules containing specific types of ISDN encoding/decoding protocols.
Preferably, the connection link is set up via an Application Resource System ARE comprising a physical link handler PLH for handling messages to and from related hardware, a signal channel handler SCH for interfacing with protocol drivers and a call supporting protocol handler PH.
In a particular embodiment of the method in accordance with the invention, the signal channel handler calls the different ISDN modules that are needed, during the encoding/decoding procedure.
Preferably, the signal channel handler SCH is provided with the generic module and the protocol specific modules, and information on the actual ISDN protocol being used during configuration of the system is stored in the SCH.
Preferably, a check is made if all information elements in a time slot has been received and that the received elements are not distorted, and a message is sent to the protocol handler PH regarding set up information together with error information.
The Application Resource System according to the invention is characterized in that it includes a signal channel handler SCH for interfacing with protocol drivers and being provided with a software structure which separates the protocol software into a generic module containing generic ISDN encoding/decoding protocols and into a protocol specific module containing specific types of ISDN encoding/decoding protocols.
Preferably, the Application Resource System also includes a physical link handler PLH for handling messages to and from related hardware and a call supporting protocol handler PH.
In an advantageous embodiment of the Application Resource System, the protocol handler PH houses a state machine, and that it is provided with software which is structured in one module covering basic calls as an user side, PH-user, one module covering basic calls as a net side, PH-net, and an additional module for each type of ISDN protocol.
The Application Resource System preferably comprises a mobility server for setting up cordless connection via radio exchange between the first terminal and the second terminal.